How to distalize with aligners?

Orthodontic tooth movement closely follows Newton’s third law of motion, whereby, every tooth movement in aligner therapy generates an equal and opposite reactive force. By choosing to implement anchorage devices, orthodontists help reduce the negative impacts of this reactive force, often manifesting as anchorage loss.

Maxillary molar distalization is a strategy that is typically applied in the non-extraction treatment of Class II molar relationships. It is mostly indicated for patients suffering from maxillary dentoalveolar protrusion or minor skeletal discrepancies.

For a long time, the anchorage device of choice to bring about distalization was the headgear. Unfortunately, this appliance requires a great deal of patient compliance. Due to this several alternatives were proposed to reduce patient cooperation while boosting treatment effectiveness. One such device was the Temporary Anchorage Device (TAD).

Is distalization possible with aligners?

Several studies have evaluated whether maxillary molar distalization is actually possible with aligners. One such study obtained lateral cephalograms from 20 subjects, all of whom underwent bilateral distalization of their maxillary dentition with Invisalign® aligners. They then observed the treatment changes. The authors were surprised to discover that aligner therapy in association with composite attachments and Class II elastics was able to distalize maxillary first molars by 2.25 mm without significant tipping and vertical movements of the crown.

The same principles adopted for maxillary molar distalization were then applied for mandibular molar distalization in the correction of Class III malocclusion with Invisalign®. This study was conducted by Malekian et al. and published in the Journal of Aligner Orthodontics. They were able to find that Invisalign® was effective in the correction of Class III malocclusion with distalization from 2 to 3 mm of mandibular molars in non-growing patients.

How is sequential distalization performed?

Sequential distalization in the treatment for Class II malocclusion is done in a way where the orthodontist can distalize one tooth at a time (as opposed to en-masse movements) in order to provide optimal anchorage. This begins with the upper second molars. Once the second molars are two-thirds of the way, then the upper first molars move back, then the premolars, and so on.

In order to maintain proper crown torque, it is important to apply buccal crown torque and lingual root torque on the upper incisors just as retraction is done on the incisors. The molars will ultimately be pitted against the rest of the dentition of the arch for anchorage. This coincides with the molars being distalized with the help of aligners. Finally, elastics are used to reinforce the anchorage and prevent anchorage loss and consequential flare of the anterior teeth.

Since anchorage is crucial in this kind of orthodontic treatment, aligners are often used alongside elastics to prevent the loss of anchorage and successful distalization.